Power Distribution in a Docking Station

1. A docking station comprising: a housing; a first connector to connect to a portable computing device; a second connector to connect to an accessory; a first circuit; and a power circuit coupled to the first connector and the second connector to provide power to the first circuit from either the portable computing device or the accessory in a first mode, and to either not provide power to the first circuit or provide power to the first circuit from the portable computing device in a second mode, wherein while in the first mode, the power circuit provides power to the first circuit from the portable computing device when a voltage provided by the portable computing device is higher than a voltage provided by the accessory, and the power circuit provides power to the first circuit from the accessory when a voltage provided by the portable computing device is lower than a voltage provided by the accessory.

2. The docking station of claim 1 wherein the second mode is an identification mode where the accessory is identified.

3. The docking station of claim 1 wherein the second mode is an authentication mode where the accessory is authenticated.

4. The docking station of claim 1 wherein the first circuit comprises a multiplexing circuit, and wherein the multiplexing circuit multiplexes signals at the second connector such that the second connector may be reversible.

5. The docking station of claim 4 wherein the power circuit comprises a low-dropout regulator coupled to the first connector and further coupled to the second connector.

6. The docking station of claim 5 wherein the power circuit further comprises a first disconnect diode between the first connector and the low-dropout regulator, a second disconnect diode between the second connector and the low-dropout regulator, and a switch between the second disconnect diode and the second connector.

7. The docking station of claim 1 wherein the first connector is a connector insert located on the housing and the second connector is a connector receptacle located in the housing.

8. The docking station of claim 1 further comprising: control circuitry coupled to the second connector to determine whether the accessory is a first type of accessory; and input power circuitry coupled between the first connector and the second connector to receive power from the portable computing device and to provide the received power to the accessory when the accessory is the first type of accessory, and otherwise to receive power from the portable computing device and provide regulated power to the accessory.

9. The docking station of claim 8 wherein the first type of accessory is an accessory having a first voltage requirement.

10. The docking station of claim 8 wherein the first type of accessory is an accessory made by a specific vendor.

11. A docking station comprising: a first connector to connect to a portable computing device; a second connector to connect to an accessory; a first circuit; a transistor having a first terminal coupled to the second connector; a first diode having an anode coupled to a second terminal of the transistor; a second diode having an anode coupled to the first connector; and a power circuit having an input coupled to a cathode of the first diode and a cathode of the second diode and an output to provide power to the first circuit.

12. The docking station of claim 11 further comprising a control circuit having an output coupled to a control terminal of the transistor wherein the control circuit identifies the accessory.

13. The docking station of claim 11 further comprising a control circuit having an output coupled to a control terminal of the transistor, wherein the control circuit authenticates the accessory.

14. The docking station of claim 13 wherein the power circuit comprises a low-dropout regulator.

15. The docking station of claim 14 further comprising: a resistor coupled between the cathodes of the first and second diodes and the input of the power circuit; and a capacitor coupled between the input of the power circuit and ground, wherein the transistor comprises a P-channel transistor where the first terminal is a drain, the second terminal is a source, and the control terminal is a gate of the transistor.

16. The docking station of claim 11 further comprising: control circuitry coupled to the second connector to determine whether the accessory is a first type of accessory; a first regulator coupled between the first connector and the second connector; and a switch coupled between an input and an output of the first regulator, wherein the switch is closed to receive power from the portable computing device and to provide the received power to the accessory when the accessory is the first type of accessory, and otherwise the switch is open such that power received from the portable computing device is regulated by the first regulator and provided to the accessory.

17. The docking station of claim 16 wherein the first type of accessory is an accessory having a first voltage requirement.

18. The docking station of claim 16 wherein the first type of accessory is an accessory made by a specific vendor.

19. A docking station comprising: a housing; a first connector located on the housing to connect to a portable computing device; a second connector located on the housing to connect to an accessory; a first circuit; and a power circuit coupled to the first connector and the second connector to provide power to the first circuit from either the portable computing device or the accessory, wherein the power circuit provides power to the first circuit from the portable computing device when a voltage provided by the portable computing device is higher than a voltage provided by the accessory, and the power circuit provides power to the first circuit from the accessory when a voltage provided by the portable computing device is lower than a voltage provided by the accessory.

20. The docking station of claim 19 further comprising: control circuitry coupled to the second connector to determine whether the accessory is a first type of accessory; and input power circuitry coupled to the first connector and the second connector to receive power from the portable computing device and to provide the received power to the accessory when the accessory is the first type of accessory, and otherwise to receive power from the portable computing device and provide regulated power to the accessory.